Compound Input

Basic Input

In the UNIFAC program, compounds are expected to be input as SMILES strings, and their ratios are expected as mole fractions. A summary of basic compound input is given below:

Flag Purpose Example
-h Produces help message $AMSBIN/unifac –help
-smiles Input molecule as SMILES sting $AMSBIN/unifac -smiles <SMILES1> <SMILES2> …
-x Input the mole fractions $AMSBIN/unifac -x <mol fraction 1> <mol fraction 2> …
-solute Specify a molecule as a solute $AMSBIN/unifac -smiles CCC -solute -smiles …
-o Write output to file $AMSBIN/unifac -o <output file> …

Note that the -smiles and -x flags are only specified one time and all information ( SMILES strings and mole fractions ) comes after these flags. It is assumed that the order of the mole fractions after the -x corresponds to the order of the SMILES strings after the -smiles flag. A simple example demonstrating an activity coefficient calculation for a mixture of three compounds is given below:

$AMSBIN/unifac -smiles CCCCCC CCCO CCCCBr -solute -x 0.2 0.3 0.5 -t ACTIVITYCOEF

The -solute flag is used to specify which compounds should be treated as solutes for the PURESOLUBILITY template. See the PURESOLUBILITY section for more information.

Physical Property Input

A number of problem templates require physical property information to be input. Physical property information should be input directly after a compound’s SMILES representation. A list of the physical property flags and examples of usage are given below:

Flag Purpose Example
-pvap Vapor pressure (bar) $AMSBIN/unifac -smiles <SMILES> -pvap 0.43 …
-tvap Temperature (K) corresponding to pvap $AMSBIN/unifac -smiles <SMILES> -tvap 320.1 …
-antoine Antoine coefficients for compound $AMSBIN/unifac -smiles <SMILES> -antoine 7.23 1504.2 246.87 …
-hfusion Enthalpy of fusion in kJ/mol $AMSBIN/unifac -smiles <SMILES> -hfusion 6.4
-meltingpoint Melting point of compound (K) $AMSBIN/unifac -smiles <SMILES> -meltingpoint 421.12

Below is an example (with synthetic antoine parameters) demonstrating the command line input for a binary mixture calculation (BINMIXCOEF) using vapor pressure estimated from the antoine parameters.

$AMSBIN/unifac -smiles "CCCCOCC" -antoine 5 1500 30 \
"CCCCCC" -antoine 6 1234 10 -t BINMIXCOEF

Additionally, we present an example for calculating the solubility of DDT in ethanol. Since DDT is a solid at room temperature, this requires us to input Enthalpy of Fusion and Melting Point data.

$AMSBIN/unifac -smiles \
"C1=CC(=CC=C1C(C2=CC=C(C=C2)Cl)C(Cl)(Cl)Cl)Cl" -hfusion 26.28 -meltingpoint 383 \
"CCO" -x 0.0 1.0 -t SOLUBILITY